Archive | 2021
Editorial: Rock Avalanches
Abstract
This Research Topic Rock Avalanches gathers high-quality original research articles, reviews and technical notes on the nature and mechanics of large rock avalanches with long run-out and associated secondary features such as lakes dammed by rock avalanche deposits. Rock avalanches have volumes of millions of m or more, and large ones have major impacts on landscapes related to their source areas, travel paths and deposits. Key questions of rock avalanches include triggers and causes, mechanisms of long runout and the morphology of the rock avalanche deposits. Seismic shaking and extreme weather events are important triggering mechanisms, but some rock avalanches lack an obvious trigger. An important causative factor is the pre-existing structure of the displaced rock mass. The mechanisms of transport depend on the slope angle and shape of the sliding surface, the nature of the substrate on which the avalanche moves and the internal deformation that the rock avalanche is undergoing. The rock type and structure of the base of the rock avalanche is in many instances of paramount importance in the motion of the disintegrating rock mass. Several possibilities of how mobility and run-out are enhanced can be envisaged: 1) a mechanically weak layer within the rock mass from which the rock avalanche broke away, 2) strain softening by disintegration near the base and within the moving rock avalanche, 3) travel on ice or water-saturated unconsolidated sediment, and 4) energy transformation due to dynamic fragmentation. Analysis of the size and distribution of fragments within rock avalanche deposits, together with deposit morphology, provide insights into the internal deformation that accompanies the motion and final emplacement of the rock avalanche. All these factors contribute to the long run-out of rock avalanches, which augment the area of impact and hence landslide hazard. This Research Topic adds to the state of knowledge of large rock avalanches and their impact on landscapes and society. It comprises contributions dealing with more generic questions of rock avalanches as well as case studies from very different places throughout the world.